Complementary use of density estimates and hunting statistics: different sides of the same story?
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The use of hunting statistics for population monitoring has often been criticized because such data are affected by several sources of error. Still, for many harvested populations, hunting statistics are the only available data source and cautious use of such data may be valuable for management. Here we assessed to what extent long-term monitoring of Svalbard rock ptarmigan spring densities and hunting statistics (bag size and proportion of juveniles in the hunting bag) reflect similar population fluctuations. We found a decreasing trend in both bag size and proportion of juveniles in the bag, but no trend in ptarmigan spring densities. However, annual fluctuations of ptarmigan spring density and bag size were correlated. Together, these time series indicate that both population abundance (bag size) and recruitment (proportion of juveniles in the bag) are decreasing, but the reproductive component fraction (density of territorial males) is not yet compromised. This biological interpretation remains, however, uncertain due to lack of hunting effort data. Monitoring programs using hunting statistics should therefore critically discuss and evaluate what the hunting statistics reflect and fine-tune the hunter data collection to obtain maximum biological relevance. Still, our results illustrate that the combination of population estimates and hunting statistics can provide more nuanced information about the population status than the density estimates alone.
KeywordsHarvest Lagopus muta Long-term monitoring Point transect sampling Time series
We thank all field assistants who have participated in the annual monitoring of the Svalbard rock ptarmigans, especially Marie Lier, Heli Routti, Øystein Overrein, and Nina A. Seifert; the Governor of Svalbard for collecting the hunting statistics, especially the Nature Management advisors Bjarte Benberg and Egil Movik; Audun Igesund and Oddveig Øien Ørvoll for graphical assistance; Gunn-Sissel Jaklin for reviewing the English language; and Arnaud Tarroux for guidance to GIS in R. Rolf Ims, Arnaud Tarroux, Øystein Overrein, and three anonymous reviewers gave helpful comments on the manuscript. Personnel costs were provided by the Fram Centre COAT initiative and the Norwegian Polar Institute. Funding for field work was provided by grants from the Amundsen Center of Arctic Research (The Arctic University of Norway), the Governor of Svalbard, the Norwegian Polar Institute, and the Svalbard Environmental Protection Fund.
Compliance with ethical standards
The hunting of Svalbard rock ptarmigans comply with the regulations in The Svalbard Environmental Protection Act. This article does not contain any studies where human participants or animals were manipulated by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
- Bech N, Beltran S, Boissier J, Allienne JF, Resseguier J, Novoa C (2012) Bird mortality related to collisions with ski-lift cables: do we estimate just the tip of the iceberg? Anim Biodivers Conserv 35:95–98Google Scholar
- Bivand R, Rundel C, Pebesma E, Hufthammer KO (2014) rgeos: Interface to Geometry Engine - Open Source (GEOS), 0.3-8 edn.,Google Scholar
- Born EW, Heilmann A, Holm LK, Laidre KL (2011) Polar bears in Northwest Greenland. An interview survey about the catch and the climate. Museum Tusculanum Press, University of Copenhagen, Denmark, CopengahenGoogle Scholar
- Buckland ST, Anderson DR, Burnham KP, Laake JL, Borchers DL, Thomas L (2001) Introduction to distance sampling: Estimating abundance of biological populations. Oxford University PressGoogle Scholar
- Buckland ST, Anderson DR, Burnham KP, Laake JL, Thomas L (2004) Advanced distance sampling. Estimating abundance of biological populations. Oxford University PressGoogle Scholar
- Carroll CJ, Merizon RA (2014) Status of grouse, ptarmigan and hare in Alaska, 2014. Alaska Department of Fish and Game. Division of Wildlife Conservation, Palmer, AlaskaGoogle Scholar
- Fuglei E, Pedersen ÅØ (2011) Svalbardrypenes trekkruter til vinterområdene. Rapport til Svalbards Miljøfond (in Norwegian)Google Scholar
- Ims RA, Jepsen JU, Stien A, Yoccoz NG (2013) Science plan for COAT: Climate Ecological Observatory for Arctic Tundra. Fram Centre, NorwayGoogle Scholar
- Løvenskiold HL (1964) Avifauna Svalbardensis vol 129. Oslo, NorwayGoogle Scholar
- Ministry of Climate and Environment (2015) Regulations relating to harvesting of the fauna on Svalbard. https://www.regjeringen.no/en/dokumenter/harvesting-fauna-svalbard/id512066/. Accessed 24.02.2015
- Overrein Ø (2014) Status for høstbare viltarter på Svalbard – Helhetlig strategi for kunnskapsinnhenting (in Norwegian). Norwegian Polar Institute, NorwayGoogle Scholar
- Pedersen ÅØ, Overrein Ø, Unander S, Fuglei E (2005) Svalbard Rock Ptarmigan (Lagopus mutus hyperboreus) – a status report. vol 125. Tromsø, NorwayGoogle Scholar
- Potapov R, Potapov E (2011) Willow and Rock Ptarmigan monitoring in Russia: An historic overview. In: Watson RT, Cade TJ, Fuller M, Hunt G, Potapov E (eds) Gyrfalcons and Ptarmigan in a Changing World, Volume II. The Peregrine Fund, Boise, Idaho, USA, pp 213–228Google Scholar
- R Core Team (2014) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, AustriaGoogle Scholar
- Ranta E, Lindström J, Lindén H, Helle P (2008) How reliable are harvesting data for analyses of spatio-temporal population dynamics? Oikos 117: 1461-1468Google Scholar
- Sandercock BK, Nilsen EB, Brøseth H, Pedersen HC (2011) Is hunting mortality additive or compensatory to natural mortality? Effects of experimental harvest on the survival and cause-specific mortality of willow ptarmigan. J Anim Ecol 80:244–258. doi: 10.1111/j.1365-2656.2010.01769.x CrossRefPubMedGoogle Scholar
- Solberg EJ, Loison A, Saether BE, Strand O (2000) Age-specific harvest mortality in a Norwegian moose Alces alces population. Wildlife Biol 6:41–52Google Scholar
- Storch I (2007b) Grouse: Status Survey and Conservation Action Plan 2006–2010. Gland, Switzerland: IUCN and Fordingbridge, UK: World Pheasant AssociationGoogle Scholar
- Sutherland WJ (2001) Sustainable exploitation: a review of principles and methods. Wildlife Biol 7:131–140Google Scholar
- Thompson WL, White GC, Gowan C (1998) Monitoring vertebrate populations. Academic PressGoogle Scholar
- Weeden RB, Theberge JB (1972) The dynamics of a fluctuating population of rock ptarmigan in Alaska. Proceedings Int Ornithologal Congress 15:90–106Google Scholar